21 of the most iconic photos ever taken. The image of a napalm scarred little girl running from her burning village in Vietnam is one of the most well known photographs in the world. Kim Phuc, the girl featured in the image, is now receiving free laser surgery to cover her scars, 40 years after that terrible day.
1 Oxygen: Specialized nerve cells within the aorta and carotid arteries called peripheral chemoreceptors monitor the oxygen concentration of the blood and feed back on the respiratory centers. 2  If the oxygen concentration in the blood decreases, they tell the respiratory centers to increase the rate and depth of breathing. This mechanism prevents damage to the lungs that would be caused by over-inflation. 2  Signals from higher brain centers: Nerve cells in the hypothalamus and cortex also influence the activity of the respiratory centers. 3  During pain or strong emotions, the hypothalamus will tell the respiratory centers to speed up.
These 10 facts about space will blow your mind. The respiratory center consists of areas of the brain that are responsible for automatic control of breathing. Nerve cells in part of the lower brain stem, known as the medulla oblongata, initiate and set the rhythm of respiration. Another area of the brain stem, called the pons, contains nerve cells that affect the breathing rate. Nerve impulses travel from these areas to the respiratory muscles, causing inspiration and expiration.